OpenSUSE and Ubuntu may be susceptible to a vulnerability in a low-level application interface recently introduced to the two Linux distributions.

Both operating systems have begun including support for the Linux x32 application binary interface (ABI) — similar to a software/code-level application programming interface (API), but at machine code level.

The x32 ABI essentially allows 32-bit applications to take advantage of 64-bit x86 architectures. For it to be enabled, however, administrators need to have enabled it while building the Linux kernel. Notable exceptions to this are OpenSUSE and Ubuntu, which had enabled it by default in their distributions.

Chrome OS security engineer Kees Cook outed the vulnerability in x32 ABI, which could allow an unprivileged user to escalate their privileges due to an arbitrary kernel write flaw.

According to Cook, the bug affects all Linux kernels since 3.4, in which the option to include x32 support was included. He has also released proof-of-concept code, showing how the vulnerability can be abused.